Regex doesn't work if less than 3 characters? about spacy HOT 2 CLOSED

Doesn't seem to be exclusive to regex:

{
  "LOWER": "4k"
}

Doesn't work either.

from spacy.

This SO answer is what I was after:

In Spacy 2.3.2, 1 1/2-inch is tokenized as ('1', 'NUM'), ('1/2-inch', 'NUM'), so there will be no match with your current patterns if you do not introduce a new, specific pattern.

from spacy.